1. Field of the Invention
The present invention relates to an acceleration sensor and a fabrication method thereof.
2. Description of the Background Art
A conventional acceleration sensor has been fabricated by forming an acceleration sensor device portion for detecting the acceleration and a control circuit portion for adjusting electrical signals output from the acceleration sensor device portion to a desired value, through different wafer processes, then attaching them to a package in an assembling step and, thereafter, electrically connecting them to each other through wire bonding. Further, such an acceleration sensor device and a control circuit have been placed laterally, as described in, for example, Japanese Patent Laying-Open No. 2005-172543.
The placement disclosed in the aforementioned publication has induced the problem of the necessity of providing a package having a size equal to or greater than the areas of both the acceleration sensor device and the control device, thereby making it difficult to reduce the size of the package.
Further, in cases where the acceleration sensor is of a capacitance type, the acceleration sensor outputs electrical signals indicative of accelerations based on the change of a capacitance. The electrical connection between the acceleration sensor and the control circuit has been established through wire bonding. Accordingly, when the wire bonding for connecting the acceleration sensor and the control circuit to each other has a greater length, there has been induced the problem of the occurrence of a redundant capacitance in the wire, thereby degrading the detection accuracy.
Furthermore, in order to realize detection accuracy which satisfies product requirements, there is a need for providing, by the acceleration sensor device, a capacitance which is sufficiently greater than the aforementioned redundant capacitance, which has caused the acceleration sensor device to have a greater area, thereby inducing the problem of difficulty of size reduction.